Not Applicable.
Feller bunchers are widely used in the logging industty for accumulating in a vertical position several freshly cut trees prior to laying down the bundle at once, to be transported to roadside by a skidder or forwarder. The feller buncher consists of a felling head mounted on a heavy-duty vehicle, such as a drive to tree or swing to tree wheeled or tracked vehicle, for high efficiency logging.
Typically, saws intended for use on feller bunchers have a large saw disc with peripheral cutting teeth. The disc is rotated in a horizontal plane below a butt plate, with the teeth exposed at the front of the butt plate. One such felling head is the Timberjack Model D567 which is the subject of U.S. patent application Ser. No. 29/088,450 filed May 22, 1998, the disclosure of which is hereby incorporated by reference. Already cut trees are supported on the butt plate and held in place by one or more articulated accumulating arms. As the blade is advanced through a tree being cut, the butt plate slides under the cut stem and the stem is stabilized by one or more harvesting arms. The method is know as xe2x80x9ccut and catchxe2x80x9d because the harvesting arms do not close until severance is complete. Typically, two harvesting arms are provided which move in unison, are vertically spaced apart and are hinged to the frame of the head to pivot about a vertical axis on one side of the frame. A single accumulating arm is typically provided, positioned vertically between the two harvesting arms and hinged to pivot about a vertical axis on the opposite side of the frame. When the cut is completed, for example by driving through the tree in the case of a drive to tree feller buncher, the harvesting arms are closed thus retaining the stem on the butt plate with those already accumulated in the pocket of the head and held by the accumulating arm. The accumulating arm is withdrawn from the bundle and brought back around the bundle, including the newly cut tree.
Other means of cutting trees with power operated means include a shear and a bar saw. A shear shears off a tree with a hydraulically powered scissors-like action. A bar saw uses teeth on an endless power driven chain to cut a tree, like the commonly available chain saw, but much larger. For example, the power input to a bar saw may be in excess of 100 hp.
Bar saws have been used in connection with a felling head or a harvesting head. A felling head cuts a tree and lays it down or drops it before cutting another tree. A harvesting head is a multi-function machine which fells the tree, using the bar saw, and then strips its branches and cuts metered lengths from the stem, also using the bar saw. In both the bar saw felling head and the bar saw harvesting head, harvesting arms hold the tree while it is being cut In both machines the arms exert an upward force on the stem to keep it from pinching the saw.
Bar saws have a number of advantages over disc saws. Cutting chains are relatively easy to maintain and inexpensive. The bar is also inexpensive, particularly in comparison to a saw disc, which is a large and expensive machined component The teeth for disc saws are also relatively large and expensive replacement items.
Accumulating saws have typically employed disc saws for cutting the tree, since the design of the disc was able to accommodate the butt plate to support the tree. See, for example, U.S. Pat. No. 5,377,731, the disclosure of which is hereby incorporated by reference. A bar saw is relatively fragile and vulnerable to damage, particularly in comparison to a disc saw, and what to do with the bar saw during accumulation and transport has been a problem. The bar must at all times be protected from the environment, and from the tree while the tree is being moved into the accumulating area, and also while laid down or dropped.
The present invention provides a bar saw accumulating head in which a bar saw and an accumulating head are combined. The bar saw cuts off the stem, and harvesting and accumulating arms move it onto a butt plate and hold it supported on the butt plate.
In one aspect, the tree being cut is clamped between a harvesting arm and a reaction arm, which support the tree while it is being cut. This clamping also enables the application of an upward force on the tree which keeps it from pinching the saw bar. After the stem is cut from the stump, the harvesting arm slides the stem over the top of the stump and from the stump onto a butt plate, while the reaction arm is relieved so as to move out of the way. The butt plate may be ramped upwardly, so that as the stem is slid back over it, the stem is elevated and biased to tip forward. After the newly cut stem is slid rearwardly by the harvesting arm, the accumulating arm is withdrawn from the already accumulated bundle and brought back around to re-secure the bundle including the newly cut stem The machine is ready to cut a new tree after the bar is swung from the home position back into the cocked position.
In another aspect, cutting is begun with the bar saw in the cocked position in which it is at the front of the butt plate and generally perpendicular to the machine direction. The chain is driven and the bar is pivoted through the tree, with the head held generally stationary. Pivoting may be through an angle of approximately 90xc2x0, to a home position. In the home position, the bar is generally parallel to the machine direction. Preferably, the bar is housed in a box in the home position, with the inner side of the box open. The bar is kept in the home position at all times, except just prior to commencing and during a cut. After the cut is made, the bar is parked in the home position where it is well protected, until just prior to the next cut. In conventional bar saws, the saw bar is typically returned to its starting position by retracting it through the kerf, which increases the chance for damage.
These and other objects and advantages of the invention will be apparent from the detailed description and drawings.